In this paper, we explore the entanglement of assistance for a
general pure tripartite state in terms of I-concurrence
[1]}. We obtain a lower bound of entanglement of
assistance, which is also the lower bound of a tripartite
entanglement measure, the entanglement of collaboration. This may
help to characterize the localizable entanglement. Furthermore, an
upper bound is also obtained. Deducing from the upper bound of
entanglement of assistance, we find a proper form of entanglement
monogamy inequality for arbitrary N-qubit states, which is analogous
to the monogamy constraints for concurrence proposed by Coffman
et al. [2]} and proven by Osborne et al.
[3]} for the general case.
